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Technical Paper

Two-Stroke Engine Design With Selective Exhaust Gas Recirculation - a Concept

1997-10-27
978493
High unburned hydrocarbon emissions and poor fuel consumption arise in a carburetted two-stroke engine because of its scavenging process. Time resolved hydrocarbon concentration at the exhaust port has shown a definite trend in concentration of unburned hydrocarbon with respect to crank angle. This paper discusses an exhaust gas recirculation system designed to trap fraction of the exhaust gas that is rich in short circuited fresh charge. In this design, the differential pressure between the crankcase and the exit at the exhaust port is communicated with each other at the appropriate time through passages in the piston and the cylinder block. The design is thus capable of selectively trapping and recirculating fraction of the exhaust gas rich in short circuited fresh charge back into the cylinder for combustion.
Technical Paper

Ceramic Coating for Aluminum Engine and Components

1996-04-01
91A105
The trend toward lighter vehicles for improved performance has recently introduced the use of aluminum and plastic materials for vehicle bodies and drive trains. In particular, the aluminum alloy block foar engine application is certain to reappear. The soft aluminum cylinder liner will require additional treatment before acceptance. Three possible approaches appear to solve the aluminum cylinder liner dilemma. These approaches are: 1) use of high silicon aluminum such as the 390 aluminum; 2) insert or cast steel liners into the aluminum engine block; and 3) ceramic coat the low cost standard aluminum engine block. Each has known advantages and disadvantages. It is the purpose of this paper to present the merits of option 3, the ceramic coated aluminum cylinder bore, from the standpoint of low weight, cost, and tribological effectiveness. The advantages of approaches 1) and 2) are obvious. High temperature after treatment of the ceramic engine components is not required.
Technical Paper

Non-Reacting and Reacting Flow Analysis in an Aero-Engine Gas Turbine Combustor Using CFD

2007-04-16
2007-01-0916
A gas turbine combustion system is an embodiment of all complexities that engineering equipment can have. The flow is three dimensional, swirling, turbulent, two phase and reacting. The design and development of combustors, until recent past, was an art than science. If one takes the route of development through experiments, it is quite time consuming and costly. Compared to the other two components viz., compressor and turbine, the combustion system is not yet completely amenable to mathematical analysis. A gas turbine combustor is both geometrically and fluid dynamically quite complex. The major challenge a combustion engineer faces is the space constraint. As the combustion chamber is sandwiched between compressor and turbine there is a limitation on the available space. The critical design aspect is in facing the aerodynamic challenges with minimum pressure drop. Accurate mathematical analysis of such a system is next to impossible.
Technical Paper

Effect Of Swirl and Tumble on the Stratified Combustion of a DISI Engine - A CFD Study

2011-04-12
2011-01-1214
Of late direct injection engines are replacing carburetted and port injected engines due to their high thermal efficiency and fuel economy. One of the reasons for the increased fuel economy is the ultra lean mixture with which the engine operates under low loads. Under the low load conditions, the air fuel ratio of the mixture near the spark plug is close to stoichiometric values while the overall mixture is lean, which is called stratified mixture. In order to achieve this, proper air motion during the late stages of compression is a must. Quality of the mixture depends on the time of injection as well as the type of fuel injector and mixture preparation strategy used. Engines employing air guided mixture preparation are considered as the second generation engines. For understanding the efficient mixture preparation method, three types of flow structures like base (low tumble), high tumble and inclined swirl are created inside the engine cylinder using shrouds on the intake valves.
Technical Paper

TACOM/Cummins Adiabatic Engine Program

1983-02-01
830314
This paper discusses the goals, progress, and future plans of the TACOM/Cummins Adiabatic Engine Program. The Adiabatic Engine concept insulates the diesel combustion chamber with high temperature materials to allow hot operation near an adiabatic operation condition. Additional power and improved efficiency derived from this concept occur because thermal energy, normally lost to the cooling and exhaust systems, is converted to useful power through the use of turbomachinery and high-temperature materials. Engine testing has repeatedly demonstrated the Adiabatic Engine to be the most fuel efficient engine in the world with multi-cylinder engine performance levels of 0.285 LB/BHP-HR (48% thermal efficiency) at 450 HP representative. Installation of an early version of the Adiabatic Engine within a military 5 ton truck has been completed, with initial vehicle evaluation successfully accomplished.
Technical Paper

Tribological Investigations for an Insulated Diesel Engine

1983-02-01
830319
A Minimum Cooled Engine (MCE) has been successfully run for 250 hours at rated condition of 298 kW and 1900 rpm. This engine was all metallic without any coolant in the block and lower part of the heads. Ring/liner/lubricant system and thermal loading on the liner at top ring reversal (TRR) as well as on the piston are presented and discussed. Ring/liner wear is given as well as oil consumption and blow-by data during the endurance run. Another engine build with a different top ring coating and several lubricants suggested that a 1500 hours endurance run of MCE is achievable. Rig test data for screening ring materials and synthetic lubricants necessary for a successful operation of a so-called Adiabatic Engine with the ring/ceramic liner (SiN) interface temperature up to 650°C are presented and discussed.
Technical Paper

Solid Lubrication Studies for Adiabatic Diesel Engines

1985-02-25
850508
A new self lubricating material has been assessed in a laboratory rig simulating high temperature piston rings for adiabatic diesel engines. The material consists of a solid metallic surface containing half millimetre diameter pockets filled with solid lubricant. The friction and wear properties of conventional piston ring surfaces were assessed at 380°C versus a chromium oxide counterface. This was followed by a study of the properties of various solid lubricant formulations which were then evaluated as fillers for surface pockets. The most promising solid lubricated materials contained molybdenum disulphide or lithium fluoride plus copper.
Technical Paper

Under the Roof of the Cylinder Head-An Experimental Study of the in-Cylinder Air Movement in a Two-Stroke Spark Ignition Engine

1986-02-01
860166
In this investigation the in-cylinder flow field structure was evaluated in a small displacement (50 CC) two-stroke spark-ignition engine using cylinders with Schnuerle-ports and a boost-port. A special hot-wire probe was designed, fabricated and calibrated for the use in this work. A constant temperature hot-wire anemometer was used for measurements. The effects of speed, throttle position and piston head shape were studied. The effect of compression ratio, silencer shape and inclusion of resonator to the engine induction and exhaust systems on the in-cylinder flow field activity in the Schnuerle-ported cylinder were analysed. The flow field conditions at different downward locations in the axial direction from the spark point were also evaluated in the Schnuerle-ported cylinder.
Technical Paper

Analysis and Test of Insulated Components for Rotary Engine

1989-02-01
890326
The two newest internal combustion engine technologies which have demonstrated the most promise in the last 25 years are the direct-injection stratified-charge (DISC) rotary engine [1] and the adiabatic diesel engine [2]. The (DISC) engine is particularly attractive for aviation applications [3] because of its light weight, multi-fuel capability and potential for low fuel consumption. However, one disadvantage with the DISC engine is the weight and size of the liquid cooling system. NASA Lewis Research Center has supported a technology enablement program to advance the DISC rotary engine for general aviation applications and recognizes the importance of improvement in fuel consumption and reductions in the coolant system weight [4].
Technical Paper

Performance of Thin Thermal Barrier Coating on Small Aluminum Block Diesel Engine

1991-02-01
910461
The cylinder of the aluminum engine block without iron sleeve was coated directly with thin thermal barrier coatings of zirconia and chrome oxide. The cylinder head and valve face and the piston crown were also coated. These three engine components were tested individually and together. The fuel consumption performance of this 84 x 70 mm direct injection diesel engine improved 10% with only coated cylinder bore. When the fuel injection timing of the coated cylinder bore engine was retarded by about 2°CA, emissions characteristics were approximately the same level as for the baseline engine with 8% improvement in brake specific fuel consumption compared with the baseline engine. At constant fuel flow rate to the engine, the exhaust and cylinder head temperatures were higher for the insulated bore case. One can summarize the combustion temperature must have been higher and heat release rates were faster in the insulated case.
Technical Paper

An Experimental Investigation of the Flow Characteristics in the Swirl Chamber of a C.I. Engine

1991-02-01
910480
The global flow characteristics such as mean velocity, turbulence intensity and scales of turbulence have been measured in a swirl combustion chamber of a Compression Ignition engine using a constant temperature hot-wire anemometer. The experiments were conducted at 400 rpm under motoring (non-firing) conditions. Ensemble averaging procedure was adopted to calculate the mean velocity and turbulence intensity after comparing the merits and demerits of this method with the Individual Cycle Mean method and the Frequency Separation method. The experimental results indicate that the mean velocity and turbulence intensity show significant spatial and temporal variations in the swirl chamber. These variations are observed to be maximum from 60 deg. bTDC to TDC of compression. The values of mean velocity at chamber periphery are found to be higher than the values near the chamber axis.
Technical Paper

High Pressure Fuel Injection for High Power Density Diesel Engines

2000-03-06
2000-01-1186
High-pressure fuel injection combustion is being applied as an approach to increase the power density of diesel engines. The high-pressure injection enables higher air utilization and thus improved smoke free low air-fuel ratio combustion is obtained. It also greatly increases the injection rate and reduces combustion duration that permits timing retard for lower peak cylinder pressure and improved emissions without a loss in fuel consumption. Optimization of these injection parameters offers increased power density opportunities. The lower air-fuel ratio is also conducive to simpler air-handling and lower pressure ratio turbocharger requirements. This paper includes laboratory data demonstrating a 26 percent increase in power density by optimizing these parameters with injection pressures to 200 mPa.
Technical Paper

Cummins–TARADCOM Adiabatic Turbocompound Engine Program

1981-02-01
810070
This paper describes the progress on the Cummins-TARADCOM adiabatic turbocompound diesel engine development program. An adiabatic diesel engine system adaptable to the use of high performance ceramics which hopefully will enable higher operating temperatures, reduced heat loss, and turbo-charged exhaust energy recovery is presented. The engine operating environments as well as the thermal and mechanical loadings of the critical engine components are covered. Design criteria are presented and techniques leading to its fulfillment are shown. The present shortcomings of the high performance ceramic design in terms of meeting reliability and insulation targets are discussed, and the needs for composite designs are shown. A ceramic design methodology for an insulated engine component is described and some of the test results are shown. Other possible future improvements such as the minimum friction-unlubricated engine through the use of ceramics are also described.
Technical Paper

Flow Field Analysis of a Carburettor Using CFD

2005-01-19
2005-26-058
The objective of present study is to predict and analyze the flow through the Carburettor for two different throttle opening conditions. The studies have been carried out by Computational Fluid Dynamics (CFD) software and the prediction has been validated with experimental data. Three dimensional geometrical models of two different throttle positions namely 50% opening and wide open throttle (100% throttle opening) were created using the commercially available software. The mesh was generated using the Tet-hybrid scheme which includes primarily of tetrahedral mesh elements but may also include hexahedral, pyramidal and wedge elements. The pressure boundary conditions are used to define the fluid pressure at the inlet and outlet of the carburettor. The steady state flow field analysis inside a carburettor has been simulated using the Multiphase mixture model and Langrangian Discrete phase model.
Technical Paper

Thin Thermal Barrier Coatings for Engines

1989-02-01
890143
Contrary to the thick thermal barrier coating approach used in adiabatic diesel engines, the authors have investigated the merits of thin coatings. Transient heat transfer analysis indicates that the temperature swings experienced at combustion chamber surfaces depend primarily on material thermophysical properties, i.e., conductivity, density, and specific heat. Thus, cyclic temperature swings should be alike whether thick or thin (less than 0.25 mm) coatings are applied, Furthermore, thin coatings would lead to lower mean component temperatures and would be easier to apply than thick coatings. The thinly-coated engine concept offers several advantages including improved volumetric efficiency, lower cylinder liner wall temperatures, improved piston-liner tribological behavior, and improved erosion-corrosion resistance and thus greater component durability.
Technical Paper

Advancements in High Temperature Cylinder Liner and Piston Ring Tribology

2000-03-06
2000-01-1237
The high temperature tribology issue for uncooled Low Heat Rejection (LHR) diesel engines where the cylinder liner piston ring interface exceeds temperatures of 225°C to 250°C has existed for decades. It is a problem that has persistently prohibited advances in non-watercooled LHR engine development. Though the problem is not specific to non-watercooled LHR diesel engines, it is the topic of this research study for the past two and one half years. In the late 1970s and throughout the 1980s, a tremendous amount of research had been placed upon the development of the LHR diesel engine. LHR engine finite element design and cycle simulation models had been generated. Many of these projected the cylinder liner piston ring top ring reversal (TRR) temperature to exceed 540°C[1]. In order for the LHR diesel to succeed, a tribological solution for these high TRR temperatures had to be developed.
Technical Paper

Simulation of Fuel-Air Interaction in a Four Stroke Four Valve Direct Injected Spark Ignition (DISI) Engine

2007-04-16
2007-01-0153
Of late Direct Injection Spark Ignition (DISI) engines are replacing the carburetted SI engines due to certain inherent advantages like uniform distribution of fuel-air mixture in all cylinders in multi cylinder engines. However the homogeneity of the mixture depends on the time of injection as well as the type of fuel injector. It is expected that late in the compression stroke the fuel-air mixture near the spark plug should be a combustible mixture. In order to achieve this, proper air motion during induction and compression is a must. Further the interaction of fuel and air from the start of injection is equally important. This paper addresses these issues. For this a CFD study has been carried out. The injection timings selected are 90, 180 and 2700 aTDC, the idea being to understand the effects of early or late injection on fuel air mixing. The appropriate governing equations are solved using finite volume method. RNG k-ε turbulence model is used for physical modelling.
Technical Paper

Low Heat Rejection From High Output Ceramic Coated Diesel Engine and Its Impact on Future Design

1993-03-01
931021
A high output experimental single cylinder diesel engine that was fully coated and insulated with a ceramic slurry coated combustion chamber was tested at full load and full speed. The cylinder liner and cylinder head mere constructed of 410 Series stainless steel and the top half of the articulated piston and the cylinder head top deck plate were made of titanium. The cylinder liner, head plate and the piston crown were coated with ceramic slurry coating. An adiabaticity of 35 percent was predicted for the insulated engine. The top ring reversal area on the cylinder liner was oil cooled. In spite of the high boost pressure ratio of 4:1, the pressure charged air was not aftercooled. No deterioration in engine volumetric efficiency was noted. At full load (260 psi BMEP) and 2600 rpm, the coolant heat rejection rate of 12 btu/hp.min. was achieved. The original engine build had coolant heat rejection of 18.3 btu/hp-min and exhaust energy heat rejection of 42.3 btu/hp-min at full load.
Technical Paper

Assessment of Thin Thermal Barrier Coatings for I.C. Engines

1995-02-01
950980
This paper investigates theoretically the effects of heat transfer characteristics, such as crank-angle phasing and wall temperature swings, on the thermodynamic efficiency of an IC engine. The objective is to illustrate the fundamental physical basis of applying thin thermal barrier coatings to improve the performance of military and commercial IC engines. A simple model illustrates how the thermal impedance and thickness of coatings can be manipulated to control heat transfer and limit the high temperatures in engine components. A friction model is also included to estimate the overall improvement in engine efficiency by the proper selection of coating thickness and material.
Technical Paper

Ceramic Coatings for Aluminum Engine Blocks

1991-09-01
911719
The trend toward lighter vehicles for improved performance has recently introduced the use of aluminum and plastic materials for vehicle bodies and drive trains. In particular, the aluminum alloy block for engine application is certain to reappear. The soft aluminum cylinder liner will require additional treatment before acceptance. Three possible approaches appear to solve the aluminum cylinder liner dilemma. These approaches are: 1. Use of high silicon aluminum such as the 390 aluminum. 2. Insert or cast steel liners into the aluminum engine block. 3. Ceramic coat the low cost standard aluminum engine block. Each has known advantages and disadvantages. It is the purpose of this paper to present the merits of Option 3, the ceramic coated aluminum cylinder bore from the standpoint of low weight, cost, and tribological effectiveness. The advantages of approaches (1) and (2) are obvious. High temperature after treatment of the ceramic engine components is not required.
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