Search Results

The work presented here seeks to compare different means of providing scavenging systems for an automotive 2-stroke engine. It follows on from previous work solely investigating uniflow scavenging systems, and aims to provide context for the results discovered there as well as to assess the benefits of a new scavenging system: the reverse-uniflow sleeve-valve. For the study the general performance of the engine was taken to be suitable to power a medium-duty truck, and all of the concepts discussed here were compared in terms of indicated fuel consumption for the same cylinder swept volume using a one-dimensional engine simulation package. In order to investigate the sleeve-valve designs layout drawings and analysis of the Rolls-Royce Crecy-type sleeve had to be undertaken.

Manufacturers of heavy-duty diesel engines are facing increasingly stringent, emission standards. These standards have motivated new research efforts towards improving the performance of diesel engines. The objective of the present program is to develop a comprehensive analytical model of the diesel combustion process that can be used to explore the influence of design changes. This will enable industry to predict the effect of these changes on engine performance and emissions. A major benefit of the successful implementation of such models is that engine development time and costs would be reduced through their use. The computer model is based on the three-dimensional KIVA-II code, with state-of-the-art submodels for spray atomization, drop breakup / coalescence, multi-component fuel vaporization, spray/wall interaction, ignition and combustion, wall heat transfer, unburned HC and NOx formation, and soot and radiation.

A quasi-dimensional computer simulation model is presented to simulate the thermodynamic and chemical processes occurring within a spark ignition engine during compression, combustion and expansion based upon the laws of thermodynamics and the theory of equilibrium. A two-zone combustion model, with a spherically expanding flame front originating from the spark location, is applied. The flame speed is calculated by the application of a turbulent entrainment propagation model. A simplified theory for the prediction of in-cylinder charge motion is proposed which calculates the mean turbulence intensity and scale at any time during the closed cycle. It is then used to describe both heat transfer and turbulent flame propagation. The model has been designed specifically for the two-stroke cycle engine and facilitates seven of the most common combustion chamber geometries. The fundamental theory is nevertheless applicable to any four-stroke cycle engine.

Trucks can carry heavy load and when applying the brakes during for example a mountain downhill or for an abrupt stop, the brake temperatures can rise significantly. Elevated temperatures in the drum brake region can reduce the braking efficiency or can even cause the brake system to fail, catch fire or even break. It therefore needs to be designed such to be able to transfer the heat out of its system by convection, conduction and/or radiation. All three heat transfer modes play an important role since the drum brakes of trucks are not much exposed to external airflow, a significant difference from disk brakes of passenger cars analyzed in previous studies. This makes it a complex heat transfer problem which is not easy to understand. Numerical methods provide insight by visualization of the different heat transfer modes. Presented is a numerical method that simulates the transient heat transfer of a truck drum brake system cooldown at constant driving speed.

In order to fulfill the technical requirements of a high-efficiency low-emissions off-road horizontal diesel engine, a unique design is proposed and optimized in this paper for the cooling water jacket structure with a forced-cooling closed-loop cooling system. The cooling water flow rate, temperature, and pressure at the inlet and several other critical locations of the cooling water jacket were measured and analyzed at different engine operating conditions for the water jacket designs. A numerical simulation model of the coolant flow and the cooling system was built and used to analyze the thermal/fluid characteristics of the coolant flow in the water jacket. The impact of different structural and packaging design parameters on coolant flow and heat transfer was investigated. The design deficiency of an original (earlier) design of the water jacket was pointed out and an improved design was proposed.

Planning for charging in transport missions is vital when commercial long-haul vehicles are to be electrified. In this planning, accurate range prediction is essential so the trucks reach their destinations as planned. The rolling resistance significantly influences truck energy consumption, often considered a simple constant or a function of vehicle speed only. This is, however, a gross simplification, especially as the tire temperature has a significant impact. At 80 km/h, a cold tire can have three times higher rolling resistance than a warm tire. A temperature-dependent rolling resistance model is proposed. The model is based on thermal networks for the temperature at four places around the tire. The model is tuned and validated using rolling resistance, tire shoulder, and tire apex temperature measurements with a truck in a climate wind tunnel with ambient temperatures ranging from -30 to 25 °C at an 80 km/h constant speed.

As a non-predictive model of the scavenging process, a generalized thermodynamic model has been suggested. This model can give a thermodynamic description for any possible scavenging process. Having specified a history of the scavenging process, this model is suitable for all scavenging systems including cross, loop and uniflow scavenging schemes. For the simplified isobaric and isochoric model with respectively constant coefficients of intake and discharge proportions during different scavengine phases, analytical solutions for this model have been obtained. From these, all existing models with the isobaric and isochoric assumptions can be derived.

A lumped-parameter thermal network model, based on the analogy between heat transfer and electric current flow, is presented for hybrid powertrain cooling systems. In order to optimally select the powertrain components that are commercially viable and meet performance, emission, fuel economy and life targets, it is necessary to consider the influence of cooling architecture. Especially in electric and hybrid vehicles, temperature monitoring is important to increase power and torque utilization while preventing thermal damages. Detailed thermal models such as FEA and CFD are considered for component level assessments as they can locate thermal hotspots and identify possible design changes needed. However, for the system level analysis, the detailed numerical models are not suitable due to the requirement of high computation effort.

The paper describes a compact low cost engine simulator used in a diagnostic system for marine diesel engines. It models normal and certain abnormal behaviour modes and can be used with an intelligent health monitor for fault recognition. The mathematical model used is the highly detailed ‘filling and emptying’ method wherein the first order equations which result from the principles of energy, mass and momentum conservation are solved on a degree by degree basis. This allows a number of faults to be simulated, for example, those which affect the airflow such as leaking intake or exhaust manifolds or fouled turbomachines or intercoolers. A multiprocessor Motorola 68020 computer system is used to allow concurrent solution of the equations for each of the thermodynamic control volumes.

To reduce heat transfer between hot gas and cavity wall, thin Zirconia (ZrO2) layer (0.5mm) on the cavity surface of a forged steel piston was firstly formed by thermal spray coating aiming higher surface temperature swing precisely synchronized with flame temperature near the wall resulting in the reduction of temperature difference. However, no apparent difference in the heat loss was analyzed. To find out the reason why the heat loss was not so improved, direct observation of flame impingement to the cavity wall was carried out with the top view visualization technique, for which one of the exhaust valves was modified to a sapphire window. Local flame behavior very close to the wall was compared by macrophotography. Numerical analysis by utilizing a three-dimensional simulation was also carried out to investigate the effect of several parameters on the heat transfer coefficient.

Presenting a brand new approach to heat exchangers for engines, transmissions, hydraulic systems, etc. This new heat exchanger is made of only two pieces of circular extruded aluminum profiles: Core and shell. No soldering: The core and the shell is assembled by a minimum of automated work. In an oil to water cooling application, the active surface on the oil side of the core is enlarged by fins 0.2 mm thick, 0.3 mm spacing, and 3 mm high. The fins are made in unique production machines and enlarge the active surface area approximately five times compared to a conventional heat exchanger of the same dimensions. The principle utilizes the low pressure drop at laminar flow and avoids the disadvantage of low heat transfer after a certain laminar flow length. The result is approximately three times higher oil heat dissipation, combined with very low oil pressure drop, compared to conventional technique.

The increase in the global warming potential and increase in the pollution rate; people tend to adopt an alternative for the internal combustion engine vehicles. And the alternative leans toward electric vehicle technology. The pure electric vehicle technology also has the limitations of lesser energy storing capacity and higher charging time; needs further improvement. The advancements are Fuel Cell Electric Vehicles (FCEV) helps the vehicles to have a higher range and lesser filling time. The efficient thermal management system in FCEV leads higher energy utilization and increased vehicle range. This paper deals with the significance of thermal management energy consumption on the range and effective working of the FCEV System.

Waste heat recovery (WHR) has been recognized as a promising technology to achieve the fuel economy and green house gas reduction goals for future heavy-duty (HD) truck diesel engines. A Rankine cycle system with ethanol as the working fluid was developed at AVL Powertrain Engineering, Inc. to investigate the fuel economy benefit from recovering waste heat from a 10.8L HD truck diesel engine. Thermodynamic analysis on this WHR system demonstrated that 5% fuel saving could be achievable. The fuel economy benefit can be further improved by optimizing the design of the WHR system components and through better utilization of the available engine waste heat. Although the WHR system was designed for a stand-alone system for the laboratory testing, all the heat exchangers were sized such that their heat transfer areas are equivalent to compact heat exchangers suitable for installation on a HD truck diesel engine.

For most rolling element bearings used in practical applications, the permissible speed is defined as the bearing speed corresponding to a certain assumed limiting operating temperature in the bearing. Prediction of bearing permissible speed requires a thermal balance analysis considering 1) bearing heat generation (or torque) and 2) the heat dissipation of the bearing system, which is a function of ambient temperature, housing material and geometry and its heat transfer parameters. Recent results of running torque measurement of needle roller bearings and other types of roller bearings have been reviewed and compared with the well known Palmgren's prediction. The experimentally based formula for bearing power loss for needle bearings is used in the heat balance analysis for determining bearing reference and permissible speed. The calculated reference speed is compared with the DIN calculated reference speed using Palmgren's formula.

As a promising solution to improve fuel efficiency of a long-haul heavy duty truck with diesel engine, organic Rankine cycle (ORC) based waste heat recovery system (WHR) by utilizing the exhaust gas from internal combustion engine has continuously drawn attention from automobile industry in recent years. The most attractive concept of ORC-based WHR system is the conversion of the thermal energy of exhaust gas recirculation (EGR) and exhaust gas from Tailpipe (EGT) to kinetic energy which is provided to the engine crankshaft. Due to a shift of the operating point of the engine by applying WHR system, the efficiency of the overall system increases and the fuel consumption reduces respectively. However, the integration of WHR system in truck is challenging by using engine cooling system as heat sink for Rankine cycle. The coolant mass flow rate influences strongly on the exhaust gas bypass which ensures a defined subcooling after condenser to avoid cavitation of pump.

Cooling phenomenon of finned-wall cylinder has been studied in an operating engine. This analysis is based on the concept that the cylinder wall is considered to be one part of the engine thermal system. That is, by cycle simulation, the heat transfer rate from gas to metals was first calculated, and then the temperature distributions in the cylinder fin were obtained by a finite element method. In the meantime, the squish effect of the hemisphere chamber is incorporated into the simulation. The temperatures could be measured continuously by means of thermocouples located at 10 measuring points in the cylinder fin of the test engine of two-stroke cycle. The results showed that the cylinder temperatures increased with increasing engine speed, and also with increasing squish ratio due to increased heat loss. In this way the agreement between the calculated and the experimental results could be checked.

In heavy duty (HD) trucks cruising on expressway, about 60% of input fuel energy is wasted as losses. So it is important to recover them to improve fuel economy of them. As a waste heat recovery system, a Rankine cycle generating system was selected. And this paper mainly reports it. In this study, engine coolant was determined as main heat source, which collected energies of an engine cooling, an EGR gas and an exhaust gas, for collecting stable energy as much as possible. And the exergy of heat source was raised by increase coolant temperature to 105 deg C. As for improving the system efficiency, saturation temperature difference was expanded by improving performance of heat exchanger and by using high pressure turbine. And a recuperator which exchanges heat in working fluid between expander outlet and evaporator inlet was installed to recover the heat of working fluid at turbine generator. Then a working fluid pump was improved to reduce power consumption of the system.

Selection of the optimum catalyst for the reformation of methanol, and static/dynamic characteristics of a spark ignition engine fueld with both gasoline and methanol reformed gas were studied. Tube test results on reforming characteristics show that a catalyst made of a base metal works best. A methanol reformer with an exhaust gas heat exchanger was used. Results show that the increase of reformed gas ratio increases the stability of combustion and extends the lean limit. It also improves thermal efficiency, owing to the reduced duration of combustion. Moreover, responses of Pmax during sudden opening/closing of the throttle valve were studied. Results indicate that the higher the reformed gas ratio, the quicker the Pmax response and the smoother the combustion process.

Low heat rejection engine (LHRE) technology reduces the heat transfer from the gases in the cylinder of an internal combustion engine by insulating the walls of the combustion chamber. This technology has the potential for gains in fuel efficiency, cooling system size decrease, the use of alternative fuels, etc. Research on many experimental LHRE's has been reported in the literature. However, these engines have used ceramic material and they have two major problems that need to be overcome. They are: (1) the need for a high temperature lubrication system, and (2) brittleness of the ceramics. To overcome these limitations, a novel LHRE design has been developed in this study. In this design, a high temperature superalloy HAYNES®230™ (USN N06230)' is used instead of ceramics, and conventional low temperature lubrication can be employed. A 3.5 HP one cylinder low heat rejection Diesel engine was developed in this study and tested for 1001 hours without failure.

A two-stage heat-release model was developed and applied to both a divided-chamber and an open-chamber diesel engine to determine the fuel burning rates and product temperatures from measured cylinder pressure-time profiles. Measured NO emission levels for several engine operating conditions were used to select the equivalence ratios of the two stages. Combustion in the first stage was taken to occur at a stoichiometric air-fuel ratio, while second-stage combustion was considered to occur at an equivalence ratio below the cylinder-averaged equivalence ratio. An empirical fit for the equivalence ratio of the second stage was determined. Good agreement between the results of this model and the corresponding single-stage model was obtained for heat-release and heat-transfer histories. The computed combustion temperatures for the rich stage were found to be consistently higher (7 to 22% on an absolute scale) than published flame-temperature measurements.