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New concepts in oxygen enrichment of the inlet air have been examined in tests on two direct injection diesel engines, showing: significant reduction in particulate emissions (nearly 80% at full load), increased thermal efficiency if injection timing control is employed, substantial reductions in exhaust smoke under most conditions, ability to burn inferior quality fuels which is economically very attractive and achivement of turbo-charged levels of output with consequential benefits of increased power/mass and improved thermal efficiency. The replacement of an engine's turbocharger and intercooling system with a smaller turbocharger and polymeric membrane elements to supply the oxygen enriched stream should allow improved transient response. NOx emission remain a problem and can only be reduced to normally aspirated engine levels at some efficiency penalty.

The 2023 FISITA White Paper (for which the author was a contributor) on managing in-service emissions and transportation options, to reduce CO2 (CO2-e or carbon footprint) from the existing vehicle fleet, proposed 6 levers which could be activated to complement the rapid transition to vehicles using only renewable energy sources. Another management opportunity reported here is optimizing the vehicle’s life in-service to minimize the life-cycle CO2 impact of a range of present and upcoming vehicles. This study of the US vehicle fleet has quite different travel and composition characteristics to European (EU27) vehicles. In addition, the embodied CO2 is based on ANL’s GREET data rather than EU27 SimaPro methodology. It is demonstrated that in-service, whole-of-life mileage has a significant influence on the optimum life cycle CO2 for BEVs and H2 fuelled FCEVs, as well as ICEs and PHEVs.

This paper compares the performance, efficiency, emissions and combustion parameters of a prototype two cylinder 430 cm3 engine which has been tested in a variety of normally aspirated (NA) modes with compression ratio (CR) variations. Experiments were completed using 98-RON pump gasoline with modes defined by alterations to the induction system, which included carburetion and port fuel injection (PFI). The results from this paper provide some insight into the CR effects for small NA spark ignition (SI) engines. This information provides future direction for the development of smaller engines as engine downsizing grows in popularity due to rising oil prices and recent carbon dioxide (CO2) emission regulations. Results are displayed in the engine speed, manifold absolute pressure (MAP) and CR domains, with engine speeds exceeding 10000 rev/min and CRs ranging from 9 to 13. Combustion analysis is also included, allowing mass fraction burn (MFB) comparison.

The hydrogen assisted jet ignition system (HAJI) replaces the spark plug of an Otto cycle engine and consists of a very small pre-chamber into which a hydrogen injector and spark plug are installed. The HAJI system allows stable combustion of very lean main-chamber hydrocarbon mixtures, leading to improved thermal efficiency and very much reduced NOx emissions. The current investigation focuses on the application of HAJI to a modern pent-roof, four valve per cylinder automotive engine. The development of a new hydrogen injection system and HAJI pre-chamber based on proprietary gasoline and diesel injectors is described. Results from injector and engine performance testing are presented in detail.

Diesel engines are used in heavy duty applications because of their high efficiency and reliability. However, their high diesel particulates and NOx emissions remain major concerns. An eight cylinder direct injection diesel engine was connected to a partial flow particulate sampling mini-dilution tunnel. Six different grades of diesel fuels were studied for their regular emissions as well as smoke and particulate emissions. Each fuel was tested at three engine speeds and full load. This paper presents the results of these tests which includes analysis of the effects of load, cetane number, 90% distillation temperature, and density for steady state conditions. A correlation was developed for converting smoke numbers in Hartridge Smoke Units (HSU) to the specific particulate emissions by evaluating results of all fuels tests. Another correlation was also developed for diesel particulates and NOx emissions trade-off.

Exhaust emission tests were performed on a fleet of vehicles comprising a range of engine technology from leaded fuel control methods to closed loop three-way catalyst meeting 1992 U.S. standards but marketed in Australia. Each vehicle was tested to 5 different driving cycles including the FTP cycles and steady speed driving. Research had shown that for hot-start operation the major driving pattern parameters which influence fuel consumption and exhaust emissions are average speed and PKE (the positive acceleration kinetic energy per unit distance). Plots from analysis of micro-trip fuel use and emissions rates from the test cycles may be presented as contours in PKE. It follows that the micro trip emissions from a range of driving cycles including, regulated e.g. FTP city and unregulated e.g. LA-92, recently developed EPA cycles or from other cities e.g. Bangkok can be superimposed.

A fleet of 17 utility, van and flat tray bodied trucks has been tested for fuel consumption and exhaust emissions over a range of drive cycles and steady state operating conditions. The influence of vehicle load on the results was included. For each vehicle the tractive force applied by the chassis dynamometer, on which testing was performed, was adjusted to match those found on the road using a new procedure. The fuel consumption results show a downward trend with model year (1.7% annum); about 30% higher petrol use compared with diesel; a cold start penalty of 3 L/100 km and over 2:1 variation for vehicles capable of identical transport task. Exhaust emissions from these rigid trucks were between 3 and 6 times greater than those of the passenger car fleet.

Oxygen-enriched air supplied to a diesel engine has significant benefits in reducing the particulate emissions of all fuels tested. A Caterpillar 3208 direct injection diesel engine was modified to operate on a wide range of fuel grades including residual fuel oils with oxygen-enriched intake air. The paper focuses on four fuels, two fuels were regular automotive distillate fuels, the third was a low emission diesel fuel and the fourth fuel had high boiling point fractions. Comparison with less extensive work on residual fuel oil is also included. Smoke and particulates decrease by up to 94% at full load with 27% oxygen concentration. Performance with oxygen addition using regular fuels showed comparable smoke and particulates to a premium priced low emission fuel used specifically in underground mines.

Hydrogen Assisted Jet Ignition (HAJI) is a novel method of maintaining combustion stability during ultra-lean operation of conventional, homogeneously charged, SI engines. When operating with HAJI above λ=2, CO and NOx emissions fall to low levels while HC emissions rise to approximately double their stoichiometric value. HC emissions were investigated by operating a HAJI equipped, optically accessible, four-valve single cylinder engine at 600 r/min, wide open throttle (WOT), and from λ=1 to λ=2.4. A fast flame ionisation detector was used to collect real time hydrocarbon concentration data from behind one of the exhaust valves, inside the HAJI pre-chamber, and from near the combustion chamber wall. Flame images were also obtained. Exhaust port sampling shows that the HC concentration during blowdown and early exhaust is increased, but the concentration at the end of exhaust is decreased.

The goal of hydrogen engine research is to achieve highest possible efficiency with low NOx emissions. This is necessary for the hydrogen car to remain competitive with the ever-improving efficiency of conventional fuel's use, to take advantage of the increased availability of hydrogen distribution for fuel cells and to achieve better range than battery electric vehicles. This paper examines the special problems of hydrogen engine combustion and ways to improve efficiency. Central to this are the effects of compression ratio (CR) and lambda (excess air ratio) and ignition system. The results demonstrate highest indicated thermal efficiency at ultra lean condition of lambda ≻ 2 and with central ignition. This need for this lean mixture is partly explained by the higher heat transfer losses.

A fast flame ionisation detector (FID) is able to measure the hydrocarbon (HC) concentration at a single point in the exhaust port. However, when sampling is conducted near the plane of the exhaust valve, these measurements are not representative of the entire port cross-section. This paper describes a multi-point extension to a standard fast FID probe, enabling the instantaneous measurement of a more representative HC concentration near the plane of the exhaust valve. Construction and use of the multi-point probe is discussed, and results are compared with standard single-point measurements.

The challenge of tough fuel consumption reduction targets and near zero NOx emission standards can be met by optimization of the full range of engine design variables. Here these are explored through an engine simulation model and the application of an optimizing algorithm that can work in discontinuous data space. The combustion model has main features that include flame propagation, the effects of turbulence, chamber shape interaction and NOx formation. Two engine configurations are used to illustrate the application of the model and optimizer. Both allow the adoption of extra lean burn possible with LPG as fuel and EGR through an external route or cam phasing. In the first the compression ratio and cam profiles are fixed, in the second study they are also optimized.

This paper presents a study of the performance of a lean burn, natural gas-fuelled, naturally aspirated, spark ignition engine for an E class vehicle. Engine performance and exhaust emissions (NO, CO, and UHC) data are first discussed. An energy balance of the engine operating at different loads and air-fuel ratios is then presented, and used to explain why engine efficiency varies with air-fuel ratio. Finally, the hot start drive cycle CO2e (CO2 equivalent) emissions are estimated for a vehicle with this engine. This shows a potential for significant reduction in vehicle greenhouse gas emissions compared to an equivalent gasoline-fuelled vehicle.

This paper presents a parametric, experimental study of the performance of gas and liquid propane injection in a spark ignition, multi-point port injected (MPI) engine. An inline, six cylinder engine is used over a wide range of speeds and torques, and the air/fuel ratio, compression ratio and injection timing are all varied. The engine was mapped at the standard compression ratio of 9.65:1 with the original, gasoline MPI system, propane gas MPI, and single point, throttle body, propane gas injection. Gas and liquid propane MPI are then tested at a compression ratio of 11.7:1. Contour plots of thermodynamic efficiency and the specific emissions of HC, NOx, CO2 and CO over the torque/speed range are presented and compared. The results show significant differences in performance between gas and liquid propane MPI injection, as well as the MPI and throttle body gas injection.

It is shown that LPG has the potential to be a main stream fuel because of its low particulate emissions and low greenhouse emission potential. The experimental study reported is directed at minimising the cost of LPG optimised engines through the use of gas phase, throttle body injection in an engine with 11.7 compression ratio up from 9.65 of the base gasoline engine. The advantages of throttle body injection, guided by CFD studies, are extension of the lean limit to lambda 1.6, where NOx is low enough to meet Euro4 emission standards without a reducing catalyst, as deduced from bench test results. Comparison is also made between throttle body and both liquid and gas phase multipoint port injection. Differences in the method of mixing significantly affect engine performance. Notable improvements in emissions and thermal efficiencies were achieved when compared with gasoline, eg.

In recent times new tools have emerged to aid the optimization of engine design. The particle swarm optimizer, used here is one of these tools. However, applying it to the optimization of the S.I. engine for high efficiency and low NOx emission has shown the preference of ultra lean burn strategy combined with high compression ratios. For combined power, efficiency and emissions benefits, there are two restricting factors, limiting the applicability of this strategy, knocking and cyclic variability. In the ultra lean region, knocking is not an important issue but the variability is a major concern. This paper demonstrates the application of a variability model to limit the search domain for the optimization program. The results show that variability constrains the possible gains in fuel consumption and emission reduction, through optimizing cam phasing, mixture and spark timing. The fuel consumption gain is reduced by about 11% relative.

HAJI (Hydrogen Assisted Jet Ignition) is an advanced combustion initiation system for otherwise standard S.I engines. It utilises the fluid mechanics of a turbulent, chemically active jet, combined with the reliability of spark igniting rich hydrogen mixtures. The result is an extremely robust ignition system, capable of developing power from an engine charged with air-fuel mixtures as lean as λ = 5. Experiments have been performed using a single cylinder engine operating on gasoline in the speed range of 600-1800 r/min. Data are presented in the form of maps which describe fuel efficiency, combustion stability and emissions with respect to load, speed, air-fuel ratio and throttle. The results are incorporated into a model of a known engine and vehicle and this is used to estimate performance over the Federal drive-cycle.

HAJI, or Hydrogen Assisted Jet Ignition, is an ignition system which uses a hot gaseous jet to initiate and stabilise combustion. HAJI allows a dramatic reduction of cyclic variability, and an extension of the lean limit of the engine to lambda 5. Improvements in cyclic variability lead to increased power output, reduced noise, wear on components and emissions. The ability to operate ultra lean gives 25% improvements in efficiency and extremely low emissions, particularly of NOx. Combustion analysis based on the fractal dimensions of the propagating flame fronts, obtained from optical flame data, support the hypothesis of enhancement of flame speeds through the presence of active chemical species. However, the relative contributions of turbulence and active species to the mechanisms of combustion enhancement realised with HAJI are not well defined. HAJI ignition has also been simulated with a comprehensive three dimensional combustion code, KIVA3.

This paper is based on extensive experimental research with lean burn, high compression ratio engines using LPG, CNG and gasoline fuels. It also builds on recent experience with highly boosted spark ignition gasoline and LPG engines and single cylinder engine research used for model calibration. The final experimental foundation is an evaluation of jet assisted ignition that generally allows a lean mixture shift of more than one unit in lambda with consequential benefits of improved thermal efficiency and close to zero NOx. The capability of an ultra lean burn spark ignition engine is described. The concept is operation at air-fuel ratios similar to the diesel engine but with essentially homogenous charge, although some stratification may be desirable. To achieve high thermal efficiency this engine has optimized compression ratio but with variable valve timing which enables reduction in the effective compression ratio when desirable.

In this paper, performance, efficiency and emission experimental results are presented from a prototype 434 cm3, highly turbocharged (TC), two cylinder engine with brake power limited to approximately 60 kW. These results are compared to current small engines found in today's automobile marketplace. A normally aspirated (NA) 1.25 liter, four cylinder, modern production engine with similar brake power output is used for comparison. Results illustrate the potential for downsized engines to significantly reduce fuel consumption while still maintaining engine performance. This has advantages in reducing vehicle running costs together with meeting tighter carbon dioxide (CO2) emission standards. Experimental results highlight the performance potential of smaller engines with intake boosting. This is demonstrated with the test engine achieving 25 bar brake mean effective pressure (BMEP).