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A liquid-phase port injection system for liquefied petroleum gas (LPG) generally consists of a fuel storage tank with extended capability of operating up to 600 psi, a fuel pump, and suitable fuel lines to and from the LPG fuel injectors mounted in the fuel rail manifold. Port injection of LPG in the liquid phase is attractive due to engine emissions and performance benefits. However, maintaining the LPG in the liquid phase at under-hood conditions and re-starting after hot soak can be difficult. Multiphase behavior within a liquid-phase LPG injection system was investigated computationally and experimentally. A commercial chemical equilibrium code (ASPEN PLUS™) was used to model various LPG compositions under operating conditions.

The Texas Project was a multi-year study of aftermarket conversions of a variety of light-duty vehicles to CNG or LPG. Emissions and fuel economy when using these fuels are compared to the results for the same vehicles operating on certification gasoline and Federal Phase 1 RFG. Since 1993, 1,040 tests were conducted on 10 models, totally 86 light-duty vehicles. The potential for each vehicle model/kit combination to attain LEV certification was assessed. Also, comparisons of emissions and fuel economy between converted vehicles when operating on gasoline and nominally identical un-converted gasoline control vehicles were analyzed. Additional evaluations were performed for a subfleet that was subjected to exhaust speciations for operation over the Federal Test Procedure cycle and also for off-cycle tests.

Trucks operating in inter-modal (drayage) operation in and around port and rail terminals, are responsible for a large proportion of the emissions of NOX, which are problematic for the air quality of the Houston and Dallas/Ft. Worth metro areas. A standard test cycle, called the Texas Dray Truck Cycle, was developed to represent the operation of heavy-duty diesel trucks in dray operations. The test cycle reflects the substantial time spent at idle (~45%) and the high intensity of the on-road portions. This test cycle was then used in the SAE J1321 test protocol to evaluate the effect on fuel consumption and NOX emissions of retrofitting dray trucks with light-weight, low-rolling resistance wide-single tires. In on-track testing, a reduction in fuel consumption of 8.7% was seen, and NOX emissions were reduced by 3.8% with the wide single tires compared to the conventional tires.

The University of Texas 2000 Ethanol Vehicle Challenge team remains focused on cold start, cold drivability, fuel economy, and emissions reduction for our 2000 Ethanol Vehicle Challenge entry. We used the stock PCM for all control functions except control of an innovative cold-start system our team designed. The primary modifications for improved emissions control involved ceramic coating of the exhaust manifolds, use of close-coupled ethanol-specific catalysts, use of a moddified version of the California Emissions Calibrated PCM, and our cold-start system that eliminates the need to overfuel the engine at the beginning of the FTP. Additionally, we eliminated EGR at high load to improve power density. Major modifications, such as increasing the compression ratio or pressure boosting, were eliminated from consideration due to cost, complexity, reliability, or emissions penalties.

An optical access engine was used to image the liquid film evaporation off the piston of a simulated direct injected gasoline engine. A directional injector probe was used to inject liquid fuel (gasoline, i-octane and n-pentane) directly onto the piston of an engine primarily fueled on propane. The engine was run at idle conditions (750 RPM and closed throttle) and at the Ford World Wide Mapping Point (1500 RPM and 262 kPa BMEP). Mie scattering images show the liquid exiting the injector probe as a stream and directly impacting the piston top. Schlieren imaging was used to show the fuel vaporizing off the piston top late in the expansion stroke and during the exhaust stroke. Previous emissions tests showed that the presence of liquid fuel on in-cylinder surfaces increases engine-out hydrocarbon emissions.

A quasi-dimensional model for a direct injection diesel engine was developed based on experiments at Sandia National Laboratory. The Sandia researchers obtained images describing diesel spray evolution, spray mixing, premixed combustion, mixing controlled combustion, soot formation, and NOx formation. Dec [1] combined all of the available images to develop a conceptual diesel combustion model to describe diesel combustion from the start of injection up to the quasi-steady form of the jet. The end of injection behavior was left undescribed in this conceptual model because no clear image was available due to the chaotic behavior of diesel combustion. A conceptual end-of-injection diesel combustion behavior model was developed to capture diesel combustion throughout its life span. The compression, expansion, and gas exchange stages are modeled via zero-dimensional single zone calculations.

The results of continuing investigations of a new type of ignitor, the railplug, are reported. Previous studies have shown that railplugs can produce a high velocity jet of plasma. Additionally, railplugs have the potential of assuring ignition under adverse conditions, such as cold start of an IDI diesel engine, because the railplug plasma can force ignition in the combustion chamber rather than relying on autoignition under cold start conditions. In this paper, engine data are presented to demonstrate the improved cold starting capability obtainable with railplugs. Data acquired using a railplug are compared to results obtained using no assist and using glow plugs. The engine used for this investigation will not start without glow plugs (or some starting aid) at temperatures below O°C, and the manufacturer's specification of the cold start limit for this engine using glow plugs is -24°C. Railplugs are able to initiate combustion at -29°C in one to two seconds with no preheating.

The Rotating Linear Engine (RLE) derives improved fuel efficiency and decreased maintenance costs via a unique lubrication design, which decreases piston assembly friction and the associated wear for heavy-duty natural gas and diesel engines. The piston ring friction exhibited on current engines accounts for 1% of total US energy consumption. The RLE is expected to reduce this friction by 50-70%, an expectation supported by hot motoring and tear-down tests on the UT single cylinder RLE prototype. Current engines have stationary liners where the oil film thins near the ends of the stroke, resulting in metal-to-metal contact. This metal-to-metal contact is the major source of both engine friction and wear, especially at high load. The RLE maintains an oil film between the piston rings and liner throughout the piston stroke due to liner rotation. This assumption has also been confirmed by recent testing of the single cylinder RLE prototype.

Ignition of extremely lean or dilute mixtures is a very challenging problem. Therefore, it is essential for the engine development engineer to understand the fundamentals and limitations of existing ignition systems. This paper presents a new railplug ignition concept, a high-energy ignition system, which can enhance ignition of very lean mixtures by means of its high-energy deposition and high velocity jet of the plasma. This paper presents initial results of tests using an inductive ignition system, a capacitor discharge ignition system, and a railplug high-energy ignition system. Discharge characteristics, such as time-resolved voltage, current, and luminous emission were measured. Spark plug and railplug ignition are compared for their effects on combustion stability of a natural gas engine. The results show that railplugs have a very strong arc-phase that can ensure the ignition of very dilute mixtures.

It is a very challenging problem to reliably ignite extremely lean mixtures, especially for the low speed, high load conditions of large-bore natural gas engines. If these engines are to be use for the distributed power generation market, it will require operation with higher boost pressures and even leaner mixtures. Both place greater demands on the ignition system. The railplug is a very promising ignition system for lean burn natural gas engines with its high-energy deposition and high velocity plasma arc. It requires care to properly design railplugs for this new application, however. For these engines, in-cylinder pressure and mixture temperature are very high at the time of ignition due to the high boost pressure. Hot spots may exist on the electrodes of the ignitor, causing pre-ignition problems. A heat transfer model is proposed in this paper to aid the railplug design. The electrode temperature was measured in an operating natural gas engine.

The On-Board Distillation System (OBDS) extracts, from gasoline, a highly volatile crank fuel that enables simultaneous reduction of start-up fuel enrichment and significant ignition timing retard during cold-starting. In a previous paper we reported reductions in catalyst light-off time of >50% and THC emissions reductions >50% over Phase I of the FTP drive cycle. The research presented herein is a further development of the OBDS concept. For this work, OBDS was improved to yield higher-quality start-up fuel. The PCM calibration was changed as well, in order to improve the response to intake manifold pressure transients. The test vehicle was tested over the 3-phase FTP, with exhaust gases speciated to determine NMOG and exhaust toxics emissions. Also, the effectiveness of OBDS at generating a suitable starting fuel from a high driveability index test gasoline was evaluated.

An original equipment gasoline-fueled 1999 Chevrolet Silverado pickup with a 5.3-liter, V8 engine was converted to operate on E85 (85% denatured ethanol and 15% gasoline). The simplest conversion of a gasoline-fueled vehicle to E85 requires modification to the fuel system, including use of components that are compatible with ethanol and fuel injectors that provide sufficient E85 for the stock engine control module (ECM) to effectively control engine operation. To retain the stock ECM, higher flow rate fuel injectors that provide approximately 40% more E85 than gasoline are required. With no engine modifications and similar engine control strategies, performance predictions show an approximate 7% torque and power increase for E85 over gasoline. The increase is primarily due to the specific energy differences between E85 and gasoline, although there should be a slight charge cooling benefit for E85 as a result of its higher heat of vaporization.

The effect of combustion chamber wall-wetting on the emissions of unburned and partially-burned hydrocarbons (HCs) from gasoline-fueled SI engines was investigated experimentally. A spark-plug mounted directional injection probe was developed to study the fate of liquid fuel which impinges on different surfaces of the combustion chamber, and to quantify its contribution to the HC emissions from direct-injected (DI) and port-fuel injected (PFI) engines. With this probe, a controlled amount of liquid fuel was deposited on a given location within the combustion chamber at a desired crank angle while the engine was operated on pre-mixed LPG. Thus, with this technique, the HC emissions due to in-cylinder wall wetting were studied independently of all other HC sources. Results from these tests show that the location where liquid fuel impinges on the combustion chamber has a very important effect on the resulting HC emissions.

The University of Texas Ethanol Vehicle Challenge team focused upon cold start/driveability, fuel economy, and emissions reduction for our 1999 Ethanol Vehicle Challenge entry. We replaced or coated all fuel system components that were not ethanol compatible. We used the stock PCM for all control functions except control of a novel cold-start system our team designed. The primary modifications for improved emissions control involved ceramic coating of the exhaust manifolds, use of close-coupled ethanol-specific catalysts, increased EGR for the operating conditions of the five longest cruises on the FTP, and our cold-start system that eliminates the need to overfuel the engine at the beginning of the FTP. This EGR control scheme should also benefit urban fuel economy. Additionally, we eliminated EGR at high load to improve power density.

A series of cold start experiments using a 2.0 liter gasoline turbocharged direct injection (GTDI) engine with custom controls and calibration were carried out using gasoline and iso-pentane fuels, to obtain the cold start emissions profiles for the first 5 firing cycles at an ambient temperature of 22°C. The exhaust gases, both emitted during the cold start firing and emitted during the cranking process right after the firing, were captured, and unburned hydrocarbon emissions (HC), CO, and CO2 on a cycle-by-cycle basis during an engine cold start were analyzed and quantified. The HCs emitted during gasoline-fueled cold starts was found to reduce significantly as the engine cycle increased, while CO and CO2 emissions were found to stay consistent for each cycle. Crankcase ventilation into the intake manifold through the positive-crankcase ventilation (PCV) valve system was found to have little effect on the emissions results.

A recently developed in-cylinder fuel injection probe was used to deposit a small amount of liquid fuel on various surfaces within the combustion chamber of a 4-valve engine that was operating predominately on liquefied petroleum gas (LPG). A fast flame ionization detector (FFID) was used to examine the engine-out emissions of unburned and partially-burned hydrocarbons (HCs). Injector shut-off was used to examine the rate of liquid fuel evaporation. The purpose of these experiments was to provide insights into the HC formation mechanism due to in-cylinder wall wetting. The variables investigated were the effects of engine operating conditions, coolant temperature, in-cylinder wetting location, and the amount of liquid wall wetting. The results of the steady state tests show that in-cylinder wall wetting is an important source of HC emissions both at idle and at a part load, cruise-type condition. The effects of wetting location present the same trend for idle and part load conditions.

To perform coastdown tests on heavy-duty trucks, both long acceleration and coasting distances are required. It is very difficult to find long flat stretches of road to conduct these tests; for a Class 8 truck loaded to 80,000 lb, about 7 miles of road is needed to complete the coastdown tests. In the present study, a method for obtaining coastdown coefficients from data taken on a road of variable grade is presented. To this end, a computer code was written to provide a fast solution for the coastdown coefficients. Class 7 and Class 8 trucks were tested with three different weight configurations: empty, “cubed-out” (fully loaded but with a payload of moderate density), and “weighed-out” (loaded to the maximum permissible weight).