Detalls of apparent temperature distributions in large ~c~le kerosene pool flames in a 2.7m square tank were measured by high-speed thermography which stores a thermal image in the form of a thermal TV color image with 25 60O data points every 0.05 seconds. The apparent temperature image can be changed to irradiance by sirnple approximations. The irradiance of the data (2 cases and 140 images) was compared with that of a wide angle thermopile radiometerto verify the data from the thermography A series of data recarded at intervals of 1 and 5 seconds were also analyzed to obtain the radiance distribution in the flame The analysis allows the following conclusions : lrradiance values obtained by high-speed therrno graphy are not very different from those of a conventional wide angle thermopile radiometer. The high radiance zone which ordinary cameras do not shaw was determined by the average vaIL~e of each of 70 apparent temperature images and the center of the high radiance zone is located at about 0.3D (D is the tank diameter) The moderately high apparent temperature range of 1323-1448K apparently has a strong influence on the irradiance of pool flames.

This　paper　describes　the　possibility　of　a　C₂H₄ concentration　monitor　using　with　the　ultrasonic　attenuations　in　mixtures of　C₂H₄ and　air. Measurements　of　the　attenuation　per　unit　distance　of 215 kHz　ultrasonic　pulses　were　carried　out　by　varying the　length　of　the　test　cell　of 34 mm　in　diameter　from 30 mm　to 300 mm. The　attenuations　of　C₂H₄ and　air　mixtures　are extremely　large　compared　with　air　and　C₂H₄．From　these　fundamental　results，the　practical　gas　detection　cells　and　the detection method　in　order　to　monitor　the　gas　concentration　were　developed．The　two 215 kHz　ultrasonic　transducers　were installed　on　the　both　sides　of　the　gas　detection　cell　of 4 mm　in　diameter　and 70 mm　or 40 mm　long．The　ultrasonic　pulses were　sent　intermittently　from　the　trallsducer　and　were　propagated　through　the　cell.　The　sound　pressure　of　the　ultmsonic waves　were　detected　by　another　transducer　on　the　other　side．　The　peek　detected　value　of　the　souod　pressure　in　the　first receiving　waves　ls　decayed　sharply　introducing　C₂H₄ and　air　mixtures　in　to　the　cell.　The　relationship　between　the　peek detected　value，P₁ and　C₂H₄ concentration，C（％）, was　measured.

The　summary　of　the　measurements　is　as　follows:

a）The peek detected value P₁ of the soud presure extremely decreases with increasing C₂H₄ concentration in a range of　C=0～20％（Fig．5 a，b）．However P₁ is　almost　constant for　a　range　of　C＞20％．The former range　is suitable for a　C₂H₄ monitor．

b）　The　gas　temperature　dependence　on　P₁　was　measured　in　a　range 1O～40℃ while　P₁ decreases　with　increasing　temperature（Fig.8），the　attenuation　per　unit　distance　is　almost　independent　of　the　temperature（Fig.9）.

c）　By　absorbing　water　vapor　into　the　gas，P₁ becomes　smaller　than　the　dry　one（Fig．5a，b）．

d）　The　C₂H₆ and　C₂H₄ gas　mixtures　were　also　investigated，The　P₁　relatively　decreases　with　increasing　C₂H₆ concentration　in　a　range　O～30％. The　C₂H₆ monitor　for　CC₂H₆ and　C₂H₄ gasmixtures　also　has　a　possibility（Fig.7〉.