Search Results

Reports published by Gulf R&D Co. and Battelle Columbus Laboratories under contract to the Coordinating Research Council's APRAC project group CAPE-24 were reviewed. Both studies failed to verify the accuracy of polynuclear aromatic hydrocarbon (PNA) emission measurements from heavy-duty diesel engines. Thermal decomposition and chemical reactions of the PNA occur in raw exhaust at temperatures above 500°F. Therefore, pipes which transfer exhaust to dilution tunnels can significantly reduce the apparent emission values. Dilution tunnel conditions have comparatively little effect on PNA measurements. However, vapor traps are required behind particle filters to assure complete collection of 4-ring PNA compounds. Guidelines are presented for controlling and testing sampling systems for accurate PNA emission measurements.

Exhaust gas recirculation (EGR) is a suitable strategy to optimize heavy duty natural gas (NG) engines. EGR could be utilized to have high specific power, with low thermal stress, but also to increase engine efficiency. NG fuelling permits a large flexibility in EGR system design, due to very clean engine exhaust. In this paper, three types of EGR routes have been studied. The best set up, which can introduce the highest EGR quantities, to provide the best reduction of the thermal load at rated power, was found to be a cooled low pressure EGR route. However high low pressure route (HLPR) could give the possibility to increase engine efficiency by modulating the power output in the widest un-throttled range operation.

This paper presents a safety mechanism that is supposed to be used to enhance in the agricultural tractors. A tractor instability situation may be occurring when drawbar force becomes large enough to cause no load (weight) on its front axle. This endangers the tractor stability and the tractor will be overturned rearward. The proposed tractor safety mechanism is based on monitoring the location of tractor center of gravity and progressively shifting forward in a dead weight to counteract for the effect of tractors front lift-up. A laboratory tractor model has been developed in such a way that the lift of its front is sensed and accordingly a mechanism that shifts a movable dead weight ahead to the front a distance that automatically ensures its longitudinal stability. Such arrangement provides a solution that practically ensures longitudinal tractor stability in the situations when maximum drawbar-pull is suddenly developed.

In any engine cooling system, de-aeration capability of the system plays a very critical role to avoid over heating of an engine. In general, with recovery bottle engine cooling system there is one vent hose from radiator pressure cap to the recovery bottle and coolant in the bottle is exposed to atmospheric pressure. From this vent hose air bubbles will move to recovery bottle from the engine and radiator when pressure in the system exceeds pressure cap setting. With this arrangement, de-aeration from the engine will happen when thermostat opens only and till that time air bubbles will be in the engine only and in this time there will be chance of overheating at some critical conditions because of air pockets in to the engine water jacket and the entrained air in the cooling circuit. Also, secondly 100 % initial filling cannot be achieved.

A sequential turbocharging method specifically developed for highly-turbocharged truck diesel engines is presented here together with the first experimental results. The key element of the method is the use of turbochargers of unequal size, with single entry turbines, in combination with a pulse converter. The first engine test showed a significant improvement of engine performance, especially of low-speed torque and response, without the usual compromise on high-speed performance. The main conclusion of the test was that with this sequential turbocharging method, engine performance is very competitive up to a bmep of 16 bar at rated power and 20 bar at peak torque.

A mathematical model has been developed which predicts the tailpipe exhaust emissions of two-stroke cycle engines utilising an oxidising catalytic converter. This model is currently one-dimensional and has been developed as an aid to the design of engine/exhaust systems. The experimental rig employed has a two-fold function, its primary task was to aid in the validation of the model. Secondary to this it was used to simulate the gaseous properties of the exhaust gas at various positions in the exhaust system. The validation exercise is currently proceeding utilising metallic substrate technology with preliminary results indicating that the model is showing good correlation to measured values.

Correlations of simply calculated fuel spray parameters with measured ISFC and smoke trends in a swirling direct injection diesel engine are described. These are based on a large number of results from experiments carried out on a 120.7 mm bore engine in which the induction swirl could be varied. The correlations indicate that (i) the fuel spray tip velocity at impingement on the chamber wall and (ii) the ‘crosswind’ over the spray at impingement have important influences. Based on these it is deduced that engine speed-related turbulence is a rate-controlling factor in DI diesel combustion.

Draft Control is a mechanism in tractors to maintain the penetration of its rear attachment (plough) in ground to avoid engine overload and keep the operation under control. The concept was introduced in excavators for controlling the cutting edge penetration of the bucket in the ground. The idea is to implement draft control automation in excavators without involving complex or expensive electronic sensors and ECUs. The proposition is to use an adjustable pressure relief valve to sense the pressure acting in the cylinder. The relief valve acts as pilot control valve to control the Boom input, thus maintaining the digging depth of the excavator bucket. The relief valve adjustment allows the user to control the bucket through different terrains, i.e., hard debris, soft soil, dust, etc. thus allowing the engine and pump to run under control conditions at all times. The potential expands to the optimizing operational efficiency with minimalistic addition of components.

New heavy-duty vehicles are simulated with the Vehicle Energy Consumption Calculation Tool (VECTO) to certify their fuel consumption and CO2 emissions in the European Union. The vehicle manufacturer runs the simulation tool and requires the vehicle components' characteristics to simulate the vehicle over standardized mission profiles. The detailed component characteristics required to run the tool are not always publicly available. In this work, a simplified model was developed to predict the fuel consumption and CO2 emissions of heavy buses over the VECTO mission profiles. It requires only the basic vehicle properties as input, such as the air drag, tire rolling resistance, mass, drivetrain efficiency and auxiliary power use. The model was derived from detailed VECTO simulations of numerous variants of a diesel high floor bus, a diesel low floor bus and a CNG low floor bus.

This paper uses a one-dimensional (1-D) simulation based approach to compare the steady state and transient performance of a Split Cycle Clean Combustion (SCCC) diesel engine to a similarly sized conventional diesel engine. Caterpillar Inc's one-dimensional modeling tool “Dynasty” is used to convert the simulation model of Caterpillar's current production turbocharged diesel engine Cat® C4.4 (used in their Hydraulic Excavator 316) to operate on the SCCC cycle. Steady state and transient engine performance is compared between the two engine variants. This study is focused only on the performance aspects of engine and relies on the other independently published papers for emissions prediction. This paper also demonstrates the use of Caterpillar's proprietary modeling software Dynasty to replicate the two cylinder SCCC engine model presented by University of Pisa in their paper [2].

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.

Carburetor engines with an inertia governor sometimes exhibit a self-excited oscillation in rotational speed, called hunting. The mechanism of hunting has been extensively studied for many years. It is our general understanding that the dynamic characteristic of the inertia governor is the primary factor to explain the phenomenon. However, the existence of another kind of hunting, called lean hunting, where lag in air-fuel ratio plays a more important role than the dynamic characteristic of the inertia governor, was reported by Tanaka(1,2). His previous papers, showing various experimental measurements of oscillating engine speed, air-fuel ratio and peak cylinder pressure, explain the nature of the phenomenon. To provide the foregoing work with a theoretical ground, we developed a mathematical formulation for the mechanism of lean hunting.

A mathematical model was developed to analyze an instability problem in a developmental motorgrader blade circuit. This dynamic computer model was verified when simulation results compared well to measured data. Solutions to the problem were found with the model. The best solution was verified with a vehicle test. This circuit included a variable pump, an implement valve, a lock valve, and a cylinder.

The conventional NOx after-treatment system could not perform sufficient NOx removal since exhaust gas temperature falls down by low-fuel-consumption and waste heat recovery of a diesel engine. In order to realize a new after-treatment system with high NOx conversion rate at a low catalyst temperature, studies on adopting an ozone generator (NO oxidization promotion) and a urea reformer (ammonia addition) into the Urea SCR (Selective Catalytic Reduction) system have been conducted.

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.

Due to stringent emission standards, the demand for higher efficiency engines has been unprecedentedly high in recent years. Among several existing combustion modes, pre-chamber spark ignition (PCSI) emerges to be a potential candidate for high-efficiency engines. Research on the pre-chamber concept exhibit higher indicated efficiency through lean limit extension while maintaining the combustion stability. In this study, a unique pre-chamber geometry was tested in a single-cylinder heavy-duty engine at low load lean conditions. The geometry features a narrow throat, which was designed to be packaged inside a commercial diesel injector pocket. The pre-chamber was fueled with methane while the main chamber was supplied with an ethanol/air mixture.

To reduce diesel engine noise that is induced mainly by main bearing impact forces, two types of low noise concepts of basic crankcase structures were studied. One is the “Isolated Skirt Type”, which has the feature to suppress vibrations of engine surface by separating the crankcase skirt from the main bearing caps. The other is the “Bed Plate Type”, which embodies the feature to suppress vibrations by stiffening the lower part of crankcase by adopting a bed plate design. Dynamic characteristics of both prototypes were investigated by means of experimental modal testings such as double pulse laser holography system and impulsive hydraulic excitation test rig which simulates the exciting force of combustion gas pressure in cylinder. As the result of many experimental tests, it was concluded that the “Bed Plate Type” was advantageous over the “Isolated Skirt Type” in terms of engine noise reduction.

The authors inserted an optical fiber into the main combustion chamber of a DI engine and led the diesel flame to the outside of the chamber. They operated the engine under various conditions and investigated into the relations between the intensity of CN band spectra in the flame, the flame temperature and the Nox concentration in the exhaust gas. As the result, a certain correlation was observed between the Nox cencentration and CN spectra, but no remarkable correlation was found between Nox and flame temperature. In view of the above facts, the Nox generation is presumably related to CN, which is an intermediate product in diesel combustion flame. IN ORDER TO MAKE CLEAR the state of combustion in diesel engines, the analysis of the phenomena must be done both in the physical and in the chemical aspects.

Interlaboratory comparisons of extraction and chemical characterization are reported for exhaust particulate from heavy-duty diesel engines, typical of the 1980s. This study is the final of a series conducted by member companies of the Coordinating Research Council on methods and measurements to expand knowledge about unregulated constituents of diesel-engine exhaust. Exhaust particulate from heavy-duty diesel engines of the 1980s averaged about 25 wt% extractable by methylene chloride. In engine-to-engine comparisons, the extractable fraction correlated with the ratio of total engine hydrocarbon to nonextractable carbon particulate. These comparative studies demonstrate methods for monitoring changes in the composition of diesel particulate that may occur as stringent emission standards are implemented in the 1990s.

A diesel engine is advantageous in its high thermal efficiency, however it still wastes about 50% of total input energy to exhaust and cooling losses. A feasibility study of thermoacoustic refrigerator was carried out as one of the means to recuperate waste heat. The thermoacoustic refrigerator prototyped for this study showed a capability to achieve cooling temperature lower than -20 degree C, which indicated that the system has a potential to be used in refrigerator trucks not only for cargo compartment cooling but also for cabin cooling.