Impact of a Non-Dedicated U-Turn on Traffic

Non-dedicated U turn has a direct effect on road safety, capacity and congestion during the traffic flow. U turn can have significant supremacy on traffic flow and headway. Therefore to study the impact of non-dedicated u turns on traffic is the ultimate requirement of the current time. This is a microscopic traffic study in which the data from a U turn (33°59’48.2"N 71°27’30.2"E) on road leading to Hayatabad and Karkhano in Peshawar is evaluated in terms of headway, speed and flow rate of traffic. Factual data is presented which shows that the average time headway surges when the traffic is interfered by the U turning vehicles. The probability density functions and cumulative density functions fit to the datasets of headway are then evaluated by the techniques of anova analysis to determine which distribution is the most suitable one for the data. Distribution data specific with the interfering U turn was taken in a separate set and evaluated. The result obtained show that the Burr Distribution and Generalized Extreme Value Distribution are the optimum to illustrate the headway data of traffic being interfered by U turning vehicles. This ligitimize the utilization of various time headway distributions of vehicles being interfered by U turning for traffic modeling.

Optimization of Dedicated Natural Gas High Comp. Spark Ignition Engine for Maximum Efficiency and Minimum Emission

All around the world the number of automobiles has increased many folds (about ten times) in the last fifty years which resulted in an enormous increase in urban pollution level especially in developing countries. Pakistan has been considered as the most urbanized country in South East Asia with about 36% of Pakistan‟s total population is residing in towns & cities. It has been estimated that an average vehicle in Pakistan emits 20 times more unburned hydrocarbons (UHCs), 24 times as much carbon monoxide (CO) & about 3.6 times more oxides of nitrogen (NOx) when compared to an average vehicle in U.S. Furthermore the scarcity of conventional fuels also propelled the world to explore alternative fuel options with same or preferably less environmental implications. Natural gas is rated as high octane alternative fuel with octane rating of 120~130 and exhibiting clean burning characteristics. It is possible to attain increased efficiency from natural gas because of its high octane value with the increase of the compression ratio of the engine. Further the improved combustion efficiency of natural gas fuel also reduces the tail pipe pollutant emission. The focus of this research is to suggest the optimum compression ratio at which the performance of dedicated natural gas engine can be optimized. A 2.5 L Diesel Engine was selected and converted to run solely on natural gas as dedicated mode by incorporating spark plugs, electronic ignition control system, and CNG fuel metering system. Different piston sets were modified to obtain selected compression ratios. Based on the literature review, compression ratios were 11, 12, 13 & 14 had been selected. The temperature gauges were installed in the cooling water circuit and exhaust manifold to measure the water & exhaust gas temperatures. The engine was then tested on dynamometer for performance & exhaust emission. The readings of NOx, CO, UHCs at 1000, 1500, 2000, 2500 and 3000 rpm at selected compression ratios were taken by using 5-gas exhaust gas analyzer. For emission testing, steady-state test profile was generated. Exhaust gas temperatures were also recorded at different rpm settings at selected compression ratios. The results have been plotted and normalized by power. Based on the engine performance, the compression ratio of 13 has been selected as optimum compression ratio for dedicated CNG engine. For further reduction of engine exhaust emission Three-Way Catalytic simulation through Chemkin software has been carried out and the performance parameters were also predicted through simulation using single-zone thermodynamic model.