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Due to the rising price of crude oil, biofuel is being considered as a global alternative for fossil fuels to reduce the emission of greenhouse gases. Diesel blended with bio fuel is currently being widely adopted in many countries. The Taiwanese government has been enforcing the adoption of B2 since 2010. However, there have remained consistent concerns about engine durability related to the use of biofuel, especially regarding after-treatment systems. A selective catalytic reduction system (SCR) has been utilized recently to reduce NOX emission in order to meet the Euro IV and V emission standards. To evaluate the impact of biodiesel on the durability of engines equipped with the SCR system, a long-term testing program was organized for the purposes of this study. The results can be used as a reference for the development of marketing promotion strategies as well as government policies in Taiwan.

Smoke is the most obvious part of the exhaust emitted from Diesel engines. The methods for smoke testing currently used in Taiwan are the rapid acceleration test under no load and the constant speed test under full load. The smoke concentration is measured with the light reflection method. According to the test procedure, the smoke meter sampling time in the rapid acceleration test is 1∼2 seconds. The current range in sampling time may cause discrepancies in test results. In these tests, free acceleration of engine is achieved by actuating the pedal rapidly. However, the speed of engine acceleration has not been defined clearly in the test procedure. The objective of this research is to study the effect of the operating conditions upon the results of smoke tests. Experiments were carried out in this study. The results of measurements showed that the opacity of the engine exhaust increased rapidly after a delay of about 0.3 seconds and then fell.

The instantaneous flow from the exhaust pipe of a single cylinder two stroke engine was studied in this research. Three exhaust pipes were investigated. One is a simple pipe with an expansion chamber, and the other two are commercial exhaust pipes. The flow field in the exhaust pipe was calculated using the one-dimensional unsteady gas dynamic model. The instantaneous velocity of the exhaust flow was detected using a hot wire anemometer located at the exit of the exhaust pipe. The calculated pressure variations inside the chambers of the exhaust pipe agreed quite well with the measured data. The calculated instantaneous exhaust velocity also matched the measured velocity variations in cases where reverse flow did not occur. However, discrepancies occurred at low engine speeds because the hot wire anemometer can not distinguish between forward and reverse flow.

Recently, due to the concern on shortage in the supply of energy source as well as the greenhouse effect of engine exhaust, the use of renewable fuel, e.g., biodiesel, in the transportation sector is promoted. However, there are distinctions on both the physical and chemical properties between biodiesel and fossil diesel. These deviations in fuel property would result in different combustion characteristics and affect the performance of exhaust aftertreatment system, including the catalytic converter and the diesel particle filter. The purpose of this study is to investigate the effect of biodiesel on the performance and the durability of diesel particle filter. The biofuel adopted in this study was obtained by transesterification from methanol and spent edible oils, and fulfills the requirements specified in EN 14214 standard. All the tests were conducted in a heavy diesel engine (ISUZU 4JJ1E4N). Two studies were carried out in this paper.

Cyclic variation is a serious problem for two stroke engines at low load conditions. The occurrence of variations seems randomly. However, there are some rough rules behind this chaotic process. The combustion of one cycle is affected by the concentration of residual gas in cylinder, which is the results of the scavenging process of pre-cycles. The objective of this paper is to study how variations occur in consecutive cycles with conventional engine cycle simulation analysis, i.e. a deterministic approach was tried to simulate a random process. The cycle model of a crankcase scavenged type single cylinder two-stroke engine was developed in this paper. The engine was divided into four sub-systems, each one is an independent thermodynamic system. Two zone combustion model was used and two different scavenging process, the perfect mixing model and the perfect displacement model, were considered in this paper.

To formulate a computer model for a two-stroke engine, the boundary conditions have to be solved for cylinder or crankcase to pipe flow, pipe flow to atmosphere. The models to deal with the former and the latter are often called partially open end model and open end model respectively. In this paper, two types of models for partially open end and two for open end are investigated by comparing the predicted pressure data in the exhaust pipe. Also, two different ways to model transfer pipe are considered. One treats the flow in transfer pipes as quasi-steady flow while the other simulates that with an one-dimensional gas dynamic model. The simulation is based on a zero-dimensional thermodynamic model for cylinder as well as crankcase and an one-dimesional gas dynamic model for pipes. The former uses 4th-order Runge-Kutta method and the latter uses a combined 4th-order Runge-Kutta and two-step Lax-Wendroff (4RK/2LW) method.

Cyclic variation is a serious problem for two stroke engines at low load conditions. Misfire and partially burned cycles occur and the unburned hydrocarbons in the exhaust are extremely high. The occurrence of variations seems random. However, there are some rules behind this seemingly chaotic process. The combustion of one cycle is affected by the concentration of residual gas in the cylinder, which is the result of the scavenging process of pre-cycles. An engine cycle model has been developed in a previous paper which can simulate the cyclically varied process and generate chaotic or multi-cycle periodic engine performance. In this paper, the engine cycle model was refined, and the calculated results of misfire rates and the HC and the CO emissions were compared with measured data. The residual gas concentration in the cylinder prior to ignition was used as the criterion to determine a successful ignition in the previous model.

Diesel engines possess high energy efficiency as for power generation, and they have been used in commercial vehicles widely for a long time. Due to the coming shortage of fossil fuel in the near future and the impact of greenhouse gas effect in recent years, the types and quantities of diesel vehicles have grown year by year. However, smoke emission of diesel engine has always been an issue. Diesel smoke can be seen by eyes apparently, and it becomes an obvious pollution problem. Traditional diesel particulate filter (DPF) is the current solution to solve the problem of smoke emission currently. However, after using DPF for a certain period of time, the back pressure of engine will rise up and the engine performance will be affected because of the accumulation of soot particles. The soot particles must be removed. This process is the regeneration of DPF.

In the development of the OBD system of a vehicle, an aged catalyst is required to test the function of the system. This catalyst is partially deteriorated and the emission after this catalyst will exceed the regulation value with limited bound according to the testing protocol. This aged catalyst is very valuable, and difficult to prepare. A bypass in the exhaust pipe was used to simulate the deterioration of catalyst in this paper to investigate the emission characteristics of a motorcycle engine. The degree of deterioration can be controlled by the portion of exhaust flow through the parallel pipe. This method of simulation has been conducted in a dynamometer testing. An electronic controlled motorcycle engine was used in this test. It was found that at low load condition, the CO and HC concentrations in the downstream of exhaust pipe were increased as the control valve was opened to let more and more exhaust to flow through the straight pipe.